Saltiness is closely connected to palatability of foods. Sodium and chlorine are essential nutrients for the human body. Common salt therefore plays an important role in seasoning, preservation, and processing of foods, and is one of the essential seasonings in the food industry. However, an excess intake of common salt is thought as a risk factor for high blood pressure and heart disease. An intake of common salt is thus strongly desired to be reduced. Reduction in intake of common salt can be achieved by reducing the content of common salt in food and drink. However, reduction of the content of common salt in food by 10% or more generally results in a bad taste.
Under such circumstances, salty taste-enhancing substances have been proposed, that can enhance the salty taste of common salt and result in satisfactory salty taste with a reduced amount of common salt used. There have been known salty taste-enhancing substances, including, for example, peptides and saturated aliphatic monocarboxylic acids having 3 to 8 carbon atoms (JP-A-63-3766, JP-A-5-184326, Biosci. Biotech. Biochem. 63, 555 (1999)).
There has been also increasing interest in physiological functions of a variety of ingredients contained in foods. Flavonoids are one kind of materials having physiological functions. Flavonoids, which are contained in vegetable foods, are known to have actions such as hypotensive, lipid metabolism improving, and allergy inhibiting actions (JP-A-8-283154, JP-A-2001-240539, JP-A-2002-47196, JP-A-2005-225847).
Flavonoids have useful physiological functions, but also have problems of low solubility in water and of producing abnormal tastes such as bitter, astringent, and harsh tastes. To address these problems, there have been known techniques of enhancing the solubility of flavonoids (JP-A-3-27293, JP-A-2000-327692, JP-A-2004-238336) and of improving tastes derived from flavonoids (JP-A-2001-309764, JP-A-2005-245291, JP-A-2005-145933). Further, techniques of applying flavonoids to foods have been proposed. For example, techniques of applying flavonoids to seasonings have been disclosed (WO 98/18348, JP-A-2000-78955, JP-A-2000-78956, JP-A-2002-291441, JP-A-2004-290129, JP-A-2005-168458). Among flavonoids, flavone, which has many methoxy residues, is known to have actions of reducing the salty taste, suppressing residual sweet taste, and the like. An action of flavonoids to enhance salty taste retention is however not known. For flavonoids, there have been disclosed actions of improving a sweet taste, reducing a strong taste of vegetable juice and an herbal drug, reducing the astringent taste and sour taste, and reducing an unfavorable taste (WO 93/10677, U.S. Pat. No. 4,031,265, U.S. Pat. No. 4,154,862, JP-A-6-335362, JP-A-8-256725, JP-A-11-318379, JP-A-2004-49186).
Liquid seasonings such as Men-tsuyu (a soup for noodles) and Ponzu (sauce that blended soy sauce and vinegar with fruit juice) are produced from soy sauce and Dashi (soup stock) as main raw materials. These have a problem that the stronger flavor of soy sauce negates the taste of Dashi and the stronger taste of Dashi brings a fishy taste derived from Dashi to spoil the flavor of the liquid seasoning. To bring out a milder flavor of a liquid seasoning, a high skill is required. To do so, a well-established Soba (buckwheat noodle) restaurant blends “Kaeshi” from soy sauce and sugar, etc., ripens it for a given time (“Nekase”) to impart a mild ripened taste, and uses it in production of a liquid seasoning. However, when a packaged men-tsuyu is industrially produced, it is actually difficult from the points of productivity and quality control that “Kaeshi” is produced and then the liquid seasoning is produced by blending “Kaeshi” and “Dashi”, followed by “Nekase” as in a well-established Soba restaurant.
To address this, soy sauces having less taste of soy sauce and suitable for Tsuyu (a soup for noodles) have been proposed (JP-A-5-115261, JP-A-9-271351, JP-A-2004-141014).
In addition, in industrial production of packaged Ponzu and the like containing highly acidic vinegar and citrus fruits juice, there are problems that less contents of vinegar and citrus fruits juice leads the stronger taste of soy sauce to kill the characteristic refreshing flavor of vinegar and citrus fruits juice and that storage stability decreases. There are also problems that excessive content of vinegar and citrus fruits juice contained leads to a stronger sour taste and/or the generation of a stuffy smell to kill the flavor of the liquid seasoning and that cost becomes high. To address this, a technique of masking an unfavorable flavor of an acidic seasoning containing citrus fruits juice and soy sauce has been disclosed (JP-A-2001-78700). The technique however has a disadvantage of reducing the sour taste as well as the unfavorable flavor of the acidic seasoning, resulting in a reduced refreshing flavor.
The present inventors have investigated flavonoids for use in liquid seasonings, and found that color tone in foods cooked with a liquid seasoning often changes in some use conditions. The present inventors have then studied for a relationship between the kind of flavonoids and color change in foods, and have found that use of a seasoning containing rutin in dishes with egg result in dishes having badly damaged appearance due to the color change of egg from natural yellow to brown.